George Bosilca wrote:
Something like this. We can play with the eager size too, maybe 4K is
too small.
george.
I guess I am curious why the larger buffer sizes work better? I am
curious because we ran into a similar issue on one of our platforms and
it turned out to be the non-temporal copy was not initiated until a
large (64K) memcpy.
--td
On Mar 18, 2009, at 06:43 , Terry Dontje wrote:
George Bosilca wrote:
The default values for the large message fragments are not optimized
for the new generation processors. This might be something to
investigate, in order to see if we can have the same bandwidth as
they do or not.
Are you suggesting bumping up the btl_sm_max_send_size value from 32K
to something greater?
--td
george.
On Mar 17, 2009, at 18:23 , Eugene Loh wrote:
A colleague of mine ran some microkernels on an 8-way Barcelona box
(Sun x2200M2 at 2.3 GHz). Here are some performance comparisons
with Scali. The performance tests are modified versions of the
HPCC pingpong tests. The OMPI version is the trunk with my
"single-queue" fixes... otherwise, OMPI latency at higher np would
be noticeably worse.
latency(ns) bandwidth(MB/s)
(8-byte msgs) (2M-byte msgs)
============= =============
np Scali OMPI Scali OMPI
2 327 661 1458 1295
4 369 670 1517 1287
8 414 758 1535 1294
OMPI latency is nearly 2x slower than Scali's. Presumably,
"fastpath" PML latency optimizations would help us a lot here.
Thankfully, our latency is flat with np with the recent
"single-queue" fixes... otherwise our high-np latency story would
be so much worse. We're behind on bandwidth as well, though not as
pitifully so.
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